"Welcome to CKAN!" on front page is untranslatable

Description

ckan/templates/home/index.html contains:

<h1 class="page_heading">Welcome to ${g.site_title}!</h1>

which means that just "Welcome to" ends up in the ckan.po files for
translation. This makes the phrase untranslatable in languages that have a different word ordering than English where the site title needs to be somewhere other than at the end of the sentence.